Variable resistance time delay circuit utilizing a coincidence circuit

ABSTRACT

Apparatus for automatically delaying operation of electronic circuits until the filaments of vacuum tubes therein are near operating temperature. A variable resistance filament receives a constant current supply. On heating, the resistance of the filament increases providing an increased voltage drop which is applied to a solid state switching device in a main gate circuit that applies an energizing signal to additional components in the system upon the coincidence of a generated pulse and the increased voltage reaching a predetermined magnitude.

United States Patent Trilling 51 Apr. 25, 1972 [54} VARIABLE RESISTANCE TIME DELAY CIRCUIT UTILIZING A COINCIDENCE CIRCUIT [56] References Cited UNITED STATES PATENTS 3,333,151 7/1967 Cannalte 315/107 [72] inventor: Ted R. Trilling, Doylestown, Pa. I I

Primary Examiner-Carl D. Quarforth [73] Assignee: The United States of America as Assistant Examiner-J. M. Potenza represented by the Secretary of the Navy Att0rney-R. S. Sciascia and Henry Hansen [22] May 20, I970 PP ,681 Apparatus for automatically delaying operation of electronic circuits until the filaments of vacuum tubes therein are near operating temperature. A variable resistance filament receives [52] U.S. Cl. ..3l5/30, 315/107, 323/38 a constant current supply on heating, the resistance of the [5 i] Int. Cl. ..I'I0l 29/52 filament increases rovidin an increased voltage dro which p s n 4 p [58] Field of Search ..315/ 102-104, 107, is applied to a solid state switching device in a mam gate cir- 315/30; 323/38 cuit that applies an energizing signal to additional components in the system upon the coincidence of a generated pulse and the increased voltage reaching a predetermined magnitude.

9 Claims, 3 Drawing Figures zs- 21 FHOSPHOR men ,5 xv PROTECTION VOLTAGE so CIRCUIT SUPPLY x2 I M /v 64 TE GENE/M T01? I a t 23 16 4/ 141 21 22 44 2 2s GATE 7 SWEEP DEFLECTION GENERATOR CIRCUIT GENERATOR AMP VIDEO 35 AMP 19 i i q 11 7 UNBLANKING GENERATOR 6.3 VDC 10 7 REGULATED POWER SUPPLY VIDEO (6.3 V.D.C.i INPUT VARIABLE RESISTANCE TIME DELAY CIRCUIT UTILIZING A COINCIDENCE CIRCUIT STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates generally to time delay devices and more particularly to systems in which the operation of a component is delayed until operating parameters have reached predetermined values for proper operation of the component.

In modern electronic circuits in which filament heating is required, such as in a cathode ray tube, the voltage regulated power supply to the filament frequently includes current limiting for protection against overload and short circuits. In addition, the circuits also include time delay relays for inhibiting electrical signals, such as to the cathode ray tube grid and anodes, until the filaments are heated to operating temperature. These relays were clock actuated or temperature responsive. In the former, a momentary break in the power supply during startup, would cause recycling and unnecessary down time. In the latter, special detectors and relays are required.

SUMMARY OF THE INVENTION Accordingly, a general purpose of the present invention is to provide for a vacuum tube device a relatively simple construction time delay circuit that takes advantage of the current limitation characteristics of certain type power supplies. 3 5 Another object is to provide a time delay that has low power consumption requirements, a high degree of reliability and no moving parts.

This is accomplished by the direct monitoring of the filament or cathode heater electrical characteristics. In particular a D.C. power supply is utilized that has regulation characteristics so that if a certain current drain is exceeded, the power supply changes from a constant voltage mode into a constant current mode or a foldback type current mode. The power supply is connected to the filament of a vacuum tube so that on heating up, the resistance of the filament increases causing the voltage drop across the filament to likewise increase. The voltage across the filament is applied to a solid state switching device that provides a switching function to permit operation of other elements within the system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block schematic diagram of an embodiment of the invention;

FIG. 2 is a schematic diagram of a gate circuit of FIG. 1; and

FIG. 3 is a diagram of typical voltage and current response of a regulated power supply of FIG. 1 during a warm-up period.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of the drawing, there is shown a D.C. regulated power supply 10. Power supply 10 is a current limiting device whose output voltage is lowered when the current drawn exceeds a predetermined magnitude. The voltage and current characteristics of two types of such power supplies, the constant current mode and foldback mode, are shown in FIG. 3. Suitable foldback current mode and constant current mode power supplies are, respectively, Model PM-6.60.750 AD manufactured by Technipowenlnc. and: Part No. 541200-130 manufactured by the Data Systems Division of Litton Systems, Inc.

Power supply 10 applies a voltage to a filament ll of cathode ray tube 12. The filament 11 is grounded at the side opposite to that receiving the voltage. The power supply 10 also supplies a signal to the gate circuit 14 of main gate generator 15. Gate circuit 14 in addition receives a pulse signal from pulse generator 16. Gate circuit 14 is a solid state device that is switched into the operating condition upon the coincidence of a negative going pulse from pulsing generator 16 and a D.C. signal of positive polarity above a predetermined voltage level from D.C. regulated supply 10. The main gate generator 15 upon being switched on supplies a signal to unblanking generator 24 whose output voltage is applied to cathode 19 of cathode ray tube 12. The main gate generator 15 also supplies an output signal to sweep generator 21 whose output is applied to deflection amplifier 22 that, in turn, supplies a signal to the deflection coils 23. The deflection amplifier 22 also provides a signal to phosphor protection circuit 26 whose output is connected to the high voltage supply circuit 27. The output of the high voltage supply is connected to both a first anode 29 and a second anode 30. A video input signal is applied to video amplifier 33 whose output is applied to the control grid 35.

The gate circuit 14 as shown in FIG. 2 has a pair of transistors 41 and 42 having their emitters connected together and joined to a resistor 43 that receives a +V voltage supply. The base of transistor 41 is connected to receive pulses from pulsing generator 16. The collector of transistor 41 is connected to supply the output signal of the gate circuit 14 on line 44 and is also connected to one side of resistor 45. The other side of resistor 45 is connected to a resistor 46 that receives a V voltage supply. The collector of transistor 42 is connected between resistors 45 and 46. The voltage from D.C. power supply 10 is applied to a voltage divider circuit comprising resistors 50 and 51 with the latter connected to ground. The base of transistor 42 is connected between the resistors 50 and 51.

The sequence of operation of cathode ray tube 12 with reference to FIGS. 1, 2 and 3 will now be explained. A supply voltage of 6.3 volts D.C. is applied to filament 11 from power supply 10. The filament 11 being cold has low resistance and starts drawing an excess amount of current from power supply 10. As can best be seen in FIG. 3 when the current drawn starts to exceed approximately 0.75 amps the power supply 10 immediately goes into a constant current mode or foldback mode of operation depending on the type of power supply used. This mode of operation limits the amount of current being drawn by lowering the supply voltage to filament 11. As filament 11 increases in temperature its resistance increases and the power supply voltage moves up along the constant current or foldback current line in FIG. 3.

This increase in the voltage supplied to filament 11 is sensed by gate circuit 14 as shown in FIG. 2 in the following manner. When the D.C. power supply voltage is low the voltage applied to the base of PNP transistor 42 of gate circuit 14 is low and as a result transistor 42 begins to conduct creating a current path from +V through resistor 43, transistor 42, and resistor 46 to V. The drop across resistor 43 is of sufficient magnitude so that transistor 41 does not conduct at this point. When the D.C. power supply voltage rises above approximately 6 volts, the base of transistor 42 receives a sufficiently positive voltage to stop conduction of transistor 42. When the conduction of transistor 42 is shut off, there is no voltage drop across resistor 43. Therefore, the voltage applied to the emitter of transistor 41 is raised and a negative going pulse 60 applied to the base of transistor 41 renders the transistor conductive. The output at the collector of transistor 41 then appears as an inverted pulse 61 to that applied to the base of transistor 41. In operation pulse 60 is always of positive polarity, even at its lowest level. Otherwise transistor 41 would conduct on a negative going pulse from pulse generator 16 regardless of the level signal that was received at the base of transistor 42 from power supply 10. The inverted pulse 61 is then applied to both sweep generator 21 and unblanking generator 26. The unblanking generator 26 supplies its output signal to cathode 19. The sweep generator 21 supplies its output signal to a deflection amplifier 22 whose output signal is in turn supplied to the deflection coils 23 of cathode ray tube 12. The output signal of deflection amplifier 22 is also applied to phosphor protection circuit 26. The output signal from phosphor protection circuit 26 is applied to high voltage supply 27. High voltage supply 27 then supplies a high voltage signal to both first anode 29 and second anode 30 on cathode ray tube 12. There is in addition a video signal placed on the control grid 35 that is independent of the time delay system.

There has therefore been shown a device in which the life of a cathode ray tube or other vacuum tube device such as a magnetron, traveling wave tube, etc. has been prolonged by providing a time delay that renders the device inoperative until the filament has been heated. In addition the costly time delays caused by a separate timing mechanism have been eliminated. The resistance of the filament which is a characteristic of the temperature of the filament has been used directly by sensing the voltage drop across the filament in order to determine the time at which sufficient heat-up has been obtained. When the voltage drop is of sufficient magnitude all components within the device are energized.

Many modifications and variations of the present invention are possible in the light of the above teachings. Accordingly, it is to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A system for delaying a signal to an electronic circuit of the type including at least one vacuum tube filament comprismg:

a current-limited D.C. power supply having an output adapted to be coupled to the filament for providing a D.C. voltage of varying amplitude; and

gating means having a first input electrically coupled to receive said D.C. power supply output and a second input adapted to receive a plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and said D.C. power supply output exceeding a predetermined voltage level.

2. A system according to claim 1 wherein said gating means further comprises:

a voltage divider circuit connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude;

a first transistor means connected to said voltage divider circuit for providing conductance upon said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and

a second transistor means connected to said first transistor means and adapted to receive said plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and the conductance of said first transistor means being inhibited.

3. A system according to claim 2 wherein said first and second transistor means being respectively first and second PNP transistors having their emitters interconnected.

4. A system according to claim 3 further comprising:

bias means of positive polarity connected to said emitters of said first and second transistors;

bias means of negative polarity connected to the collectors of said first and second transistors;

said first transistor having a base connected to said voltage divider circuit;

said second PNP transistor having a base adapted to receive said plurality of electrical pulses; and

an electronic circuit connected to said second transistor collector for receiving said output pulses.

5. A vacuum tube system comprising:

a current-limited D.C. power supply for providing a first signal with a D.C. voltage of positive polarity and varying amplitude;

a filament connected to receive said first signal;

pulse generating means for generating a second signal that is a plurality of negative going pulses; gating means having a first input electrically coupled to said power supply output to receive said first signal and a second input electrically coupled to said pulse generating means to receive said second signal for providing an output signal generated by said second signal and independent of said first signal upon said first signal exceeding a predetermined voltage level and the coincidence of said first and second signals;

energizing means connected to receive said output signal and for providing voltage signals upon receipt of said output signals; and

vacuum tube anodes connected to receive said voltage signals.

6. A vacuum tube system according to claim 5 wherein said gating means further comprises:

a voltage divider connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude;

a first transistor means connected to said voltage divider circuit for providing conductance upon said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and

a second transistor means connected to said first transistor means and adapted to receive said plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and the conductance of said first transistor means being inhibited.

7. A vacuum tube system according to claim 6 wherein said first and second transistor means being respectively first and second PNP transistors having their emitters interconnected.

8. A vacuum tube system according to claim 7 further comprising:

bias means of positive polarity connected to said emitters of said first and second transistors;

bias means of negative polarity connected to the collectors of said first and second transistors;

said first transistor having a base connected to said voltage divider circuit; and

said second transistor having a base connected to receive said second signal.

9. In combination with a vacuum tube system of the type with a current-limited D.C. power supply having a voltage of varying amplitude applied to a vacuum tube filament and a signal generated for supplying power to electrodes within the vacuum tube, wherein the improvement comprises:

a voltage divider circuit connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude;

a first transistor means connected to said voltage divider circuit for providing conductance on said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and

a second transistor means connected to said first transistor means and to said signal generator for providing a signal to said signal generator to initiate power to said electrodes upon receipt of pulse signals when said D.C. voltage varying amplitude being above said predetermined level. 

1. A system for delaying a signal to an electronic circuit of the type including at least one vacuum tube filament comprising: a current-limited D.C. power supply having an output adapted to be coupled to the filament for providing a D.C. voltage of varying amplitude; and gating means having a first input electrically coupled to receive said D.C. power supply output and a second input adapted to receive a plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and said D.C. power supply output exceeding a predetermined voltage level.
 2. A system according to claim 1 wherein said gating means further comprises: a voltage divider circuit connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude; a first transistor means connected to said voltage divider circuit for providing conductance upon said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and a second transistor means connected to said first transistor means and adapted to receive said plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and the conductance of said first transistor means being inhibited.
 3. A system according to claim 2 wherein said first and second transistor means being respectively first and second PNP transistors having their emitters interconnected.
 4. A system according to claim 3 further comprising: bias means of positive polarity connected to said emitters of said first and second transistors; bias means of negative polarity connected to the collectors of said first and second transistors; said first transistor having a base connected to said voltage divider circuit; said second PNP transistor having a base adapted to receive said plurality of electrical pulses; and an electronic circuit connected to said second transistor collector for receiving said output pulses.
 5. A vacuum tube system comprising: a current-limited D.C. power supply for providing a first signal with a D.C. voltage of positive polarity and varying amplitude; a filament connected to receive said first signal; pulse generating means for generating a second signal that is a plurality of negative going pulses; gating means having a first input electrically coupled to said power supply output to receive said first signal and a second input electrically coupled to said pulse generating means to receive said second signal for providing an output signal generated by said second signal and independent of said first signal upon said first signal exceeding a predetermined voltage level and the coincidence of said first and second signals; energizing means connected to receive said output signal and for providing voltage signals upon receipt of said output signals; and vacuum tube anodes connected to receive said voltage signals.
 6. A vacuum tube system according to claim 5 wherein said gating means further comprises: a voltage divider connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude; a first transistor means connected to said voltage divider circuit for providing conductance upon said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and a second transistor means connected to said first transistor means and adapted to receive said plurality of electrical pulses for providing output pulses upon the coincidence of receiving said electrical pulses and the conductance of said first transistor means being inhibited.
 7. A vacuum tube system according to claim 6 wherein said first and second transistor means being respectively first and second PNP transistors having their emitters interconnected.
 8. A vacuum tube system according to claim 7 further comprising: bias means of positive polarity connected to said emitters of said first and second transistors; bias means of negative polarity connected to the collectors of said first and second transistors; said first transistor having a base connected to said voltage divider circuit; and said second transistor having a base connected to receive said second signal.
 9. In combination with a vacuum tube system of the type with a current-limited D.C. power supply having a voltage of varying amplitude applied to a vacuum tube filament and a signal generated for supplying power to electrodes within the vacuum tube, wherein the improvement comprises: a voltage divider circuit connected to said D.C. power supply for receiving said D.C. voltage of varying amplitude; a first transistor means connected to said voltage divider circuit for providing conductance on said D.C. voltage varying amplitude being below a predetermined level and inhibiting conductance otherwise; and a second transistor means connected to said first transistor means and to said signal generator for providing a signal to said signal generator to initiate power to said electrodes upon receipt of pulse signals when said D.C. voltage varying amplitude being above said predetermined level. 